Resonant converters may convert an input voltage to an output voltage. At start-up, the voltage of a resonant capacitor may be unpredictable. For example, during resonant converter switching operations, the voltage of the resonant capacitor may vary between a low voltage level and a high voltage level. If the resonant capacitor stops operating (e.g., power-off or trigging of a protection mechanism), the switching operation of a bridge circuit may be disabled. At this moment, the value of the voltage of the resonant capacitor may be unknown causing it to be unpredictable as subsequent start-up.